Preliminary work in our laboratory has established the presence of an unidentified spasmolytic compound in marine mollusks (Nudibranchia). The substance appears to be a low molecular weight, water-soluble, heat stable compound. It relaxes spasms produced by acetylcholine and histamine in mammalian intestinal smooth muscle and antagonizes acetylcholine contractions. In addition to a detailed study of its antimuscarinic action on intestinal smooth muscle, we propose to establish whether it blocks at autonomic ganglia or at skeletal neuromuscular junctions. We will pursue the isolation, purification and chemical identification of the active component. This will be followed by studies aimed at proof of structure using spectroscopic methods, 13C and 1H NMR, mass spectra and X-ray analysis if appropriate.